The present invention provides improvements in dairy products especially cultured dairy products such as stirred style yogurt. The improvement provides aerated or whipped yogurt products and methods of preparing such improved whipped yogurt products.
The improvement resides in part in the pre-fermentation or post fermentation addition of an improved hydrated emulsifier blend to cultured yogurt for improved aeration. A good description of such a hydrated emulsifier blend and methods for preparing is contained in commonly assigned “Food Products and Their Methods of Preparation” filed Mar. 21, 2003 to Engesser et al. Ser. No. 10/393,838 which is incorporated herein by reference.
Yogurt is a nutritious popular dairy product. At retail, yogurt is now available in a wide assortment of varieties of texture, fat content, sweetener type and level, and flavor among other attributes. Other than aseptically packaged yogurt, yogurt is traditionally distributed and consumed with a live culture that requires refrigerated distribution (2° C. to 10° C.).
From a yogurt manufacturing process standpoint, all yogurts fall into one of two styles; namely, 1) set yogurts, and 2) stirred style. The present invention finds particular suitability for use in connection with the provision of stirred style yogurts. Within these broad two classifications, numerous yogurt varieties exist.
In the set style, the manufacturer fills cups or containers with an inoculated but unfermented milk base and queiscently holds the filled cups at warm temperatures (≈40° C. to 50° C.) to allow the yogurt to ferment therein. After the desired fermenting or maturing time, the product is cooled which arrests the culturing activity and also allows the body to set to form the gel-type texture. Set style yogurts have a relatively low initial viscosity (i.e., upon filling of its food package container) and a higher temperature (“temperature of filling”) compared to the viscosity of stirred style yogurt products. As the product ferments and then is cooled, its viscosity increases to its final viscosity value. A set style yogurt is characterized by a more firm, gel-like consistency and a higher final viscosity than most stirred style yogurts. In addition to the natural thickening effect of the yogurt culture, a wide variety of thickeners and stabilizers are taught as useful to supplement the yogurt's gel characteristics.
Of course, within this set style, there is a continuum of body firmness. Most set custard style products have quite firm gels although some others are much softer. One variety of a set style yogurt is a “custard” style yogurt. The softer gel products may even be perceived by the consumer as being thinner than even certain stirred style products.
One popular style variant of custard style yogurt is fruit-on-the-bottom, also colloquially referred to as “sundae” style, in which a discrete layer of fruit preserves is on the bottom of the yogurt container and the custard yogurt fills the rest of the container. Fruit on the top style products are similarly prepared, except that the containers are typically inverted after having been allowed to set. Typically, the yogurt phase is unflavored, although occasionally sweetened, and of a white or natural color. This white color is in contrast to the separate fruit preserve layer which often contains additional coloring supplemental to that coloring provided by the ingredients of the fruit preserves. Other than for moisture equilibration, the yogurt layer and the fruit preserve layer usually do not intermix over time due to specific growth difference and the binding effect of pectin in the fruit preserves.
In the second general category of yogurt products, the yogurt is of a stirred type. In producing stirred yogurt products, the manufacturer 1) ferments an inoculated milk base in bulk, e.g., in large stirred fermentation or culturing tanks, 2) cools the yogurt so formed to arrest the fermentation, and then 3) fills the individual yogurt container with thickened yogurt. Such production facilities are run in a continuous or semi-continuous manner. More specifically, after fermentation to desired acidity and thickness, the yogurt is pumped through cooling heat exchangers to arrest the fermentation. Alternatively, the yogurt can be cooled in a two stage process to reduce shear and maximise the viscosity of the product. In a two stage process the yogurt can be first cooled to 70° F.(21° C.) via a cooling plate, thereafter the yogurt can be cooled to 40° F.(4° C.) via a cooling tunnel. Flavorings and sweeteners can be admixed with the cooled yogurt and the yogurt is charged to containers. Care needs to be taken to minimize the shear imparted to the yogurt in practicing such process steps to minimize the loss of thickness or viscosity built up by the fermentation step. Thus, the stirred style yogurt typically has a higher viscosity than set style yogurts upon filling due to the lower temperature and the thickening affect of yogurt culture. Nonetheless, the stirred style yogurt typically builds or increases substantially in viscosity after filling over time until reaching its intended finish viscosity. Of course, stirred yogurts also come in various styles and product variations.
Most commonly, fruit preserves or purees are stirred into the stirred yogurt immediately prior to filling. Such stirred style yogurts comprising intermixed fruit purees are sometimes referred to most frequently as “Swiss” style or, less frequently but equivalently as “Continental” or “French” style. Occasionally, stirred Swiss style yogurts are formulated with excessive amounts of stabilizers with the result that after upon refrigerated storage for 48 hours, the yogurt possesses a solid-like consistency, somewhat reminiscent of custard style yogurt.
As can be appreciated from the above description of the numerous styles and flavors within styles of yogurts, product proliferation and differentiation is an important characteristic of commercial yogurt manufacture. In this highly competitive food product category, there is a continuing desire to develop novel products having distinctive visual, taste, and textural variations in order to stimulate interest in yogurt sales. Current consumer trends favor “light” products, i.e., products of lower fat and/or calorie content.
In particular, it is believed that many consumers will find aesthetically attractive yogurts having a light or aerated texture. Aerated or whipped yogurts can be characterized as having a density reduced from a native range of 1.1 to 1.2 g/cc (depending upon sugar content, fruit content, etc.) to a range of 0.30 g/cc to 1.0 g/cc.
Three primary difficulties are presented by the development of such an aerated cultured dairy product characterized by having reduced density.
First, unlike frozen dairy products such as ice cream or some aerated frozen yogurt or frozen yogurt containing products, conventional yogurt products are unfrozen and are distributed under refrigerated conditions. As a result of the storage temperature, the foam created by aeration is less stable in a refrigerated yogurt product. Conventionally, yogurt enjoy about a 40 to 60 day refrigerated shelf life. Over this shelf life, the aerated yogurt can exhibit undesirable air cell coalescence leading to larger gas cells and even some collapse of the foam.
Second, additives generally employed to increase initial foam volume in food products such as ready-to-spread frostings, other refrigerated milk products, fermented and unfermented soy, rice and nut milk products, beverages and whipped toppings are less stable than the hydrated emulsifier blend used in this invention. For example, additives such as proteins, hydrocolloids, and other emulsifiers are less stable and can exhibit undesirable air cell coalescence leading to some collapse of the foam in contrast to the hydrated emulsifier blend used in this invention.
Third, additives employed to increase initial foam volume and stability over time should not adversely affect other flavor and texture attributes. Notably, proteins added for aeration purposes create an off-flavor in cultured dairy products.
Such hydrated emulsifier blends added to cultured dairy products as described in this invention desirably do not inhibit fermentation times if added post fermentation in product production. Special care must be taken in the formulation and processing of the inoculated milk base to minimize the inhibition of culture growth. Even minor increases in fermentation times reducing rates of production can have disproportionate financial consequences in large scale continuous yogurt production.
Another object of the present invention is to provide stirred style yogurts in the form of aerated yogurts.
Surprisingly, the above limitations and difficulties have now been overcome and the present invention satisfies the above objectives and a long felt need to develop aerated yogurt products for refrigerated distribution with minimal yogurt gel and foam destabilization problems. The present yogurt products are admixed with selected emulsifiers and stabilizers to provide filling and final viscosities and densities within specified ranges. In the preferred embodiment, the present methods reside importantly in part in the preferred post fermentation addition of a hydrated emulsifier blend to yogurt products but prior to aeration.
These and other objects will become increasingly apparent by reference to the following description.